Heat exchanger including multiple tube distributor

ABSTRACT

A heat exchanger includes tubes and an inlet manifold to direct a first fluid into the tubes at a third direction. Heat is exchanged between the first fluid and a second fluid in the tubes. The heat exchanger also includes a distributor tube located within the inlet manifold. The distributor tube includes a short tube including a plurality of first orifices that direct the first fluid into the inlet manifold at a first direction, and a long tube including a plurality of second orifices that direct the first fluid into the inlet manifold at a second direction.

BACKGROUND OF THE INVENTION

This invention relates generally to a microchannel heat exchanger including an inlet manifold and a distributor tube.

A microchannel heat exchanger (MCHX) includes flat tubes that extend between an inlet manifold and an outlet manifold. Refrigerant flows through the flat tubes and exchanges heat with air that passes over the tubes.

Maldistribution of two-phase refrigerant in the flat tubes can be a problem. A distributor tube can be used to decrease maldistribution of the refrigerant in the inlet manifold. The distributor tube includes an inlet, an outlet and orifices. Refrigerant enters the tube through the inlet, and the outlet is blocked to discharge the refrigerant through the orifices. The build-up of pressure in the distributor tube causes the refrigerant to equally distribute along the length of the distributor tube. The orifices are appropriately sized to cause a pressure drop or build-up in the distributor tube. The distributor tube and the orifices are also sized appropriately to reduce the amount of separation of vapor refrigerant and liquid refrigerant in the two-phase refrigerant flow.

However, when the inlet manifold is long (such as greater than 800 mm), the pressure drop along the length of the distributor tube will be uneven, and the refrigerant will not equally distribute along the length of the distributor tube.

SUMMARY OF THE INVENTION

Exemplary embodiments of the invention include a heat exchanger including tubes and an inlet manifold to direct a first fluid into the tubes at a third direction. Heat is exchanged between the first fluid and a second fluid in the tubes. The heat exchanger also includes a distributor tube located within the inlet manifold. The distributor tube includes a short tube including a plurality of first orifices that direct the first fluid into the inlet manifold at a first direction, and a long tube including a plurality of second orifices that direct the first fluid into the inlet manifold at a second direction.

Further exemplary embodiments include a refrigerant system including a compressor for compressing a refrigerant, a condenser for cooling the refrigerant, an expansion device for expanding the refrigerant, and a microchannel evaporator for heating the refrigerant. The microchannel evaporator includes tubes, an inlet manifold to direct the refrigerant into the tubes at a third direction, and a distributor tube located within the inlet manifold. The distributor tube includes a short tube including a plurality of first orifices that direct the refrigerant into the inlet manifold at a first direction and a long tube including a plurality of second orifices that direct the refrigerant into the inlet manifold at a second direction.

These and other features of the present invention will be best understood from the following specification and drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The various features and advantages of the invention will become apparent to those skilled in the art from the following detailed description of the currently preferred embodiment. The drawings that accompany the detailed description can be briefly described as follows:

FIG. 1 illustrates a prior art refrigeration system;

FIG. 2 illustrates a microchannel evaporator;

FIG. 3 illustrates a side view of a distributor tube;

FIG. 4 illustrates a perspective view of an inlet manifold with the distributor tube shown in phantom; and

FIG. 5 illustrates a cross-sectional view of the inlet manifold taken along line 5-5 of FIG. 4.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 illustrates a refrigeration system 20 including a compressor 22, a condenser 24, an expansion device 26, and an evaporator 28. Both the condenser 24 and the evaporator 28 are heat exchangers and may be microchannel heat exchangers. In the example shown, the evaporator 28 is the microchannel heat exchanger. Refrigerant circulates through the closed circuit refrigeration system 20.

A heat pump 35 can be employed to reverse the flow of the refrigerant through the refrigeration system 20. When the heat pump 35 operates, the evaporator 28 functions as a condenser, and the condenser 24 functions as an evaporator.

The refrigerant exits the compressor 22 at a high pressure and a high enthalpy and flows through the condenser 24. In the condenser 24, the refrigerant rejects heat to air and exits the condenser 24 at a low enthalpy and a high pressure. A fan 30 directs the air through the condenser 24. The cooled refrigerant then passes through the expansion device 26, expanding the refrigerant to a low pressure. After expansion, the refrigerant flows through the evaporator 28. In the evaporator 28, the refrigerant accepts heat from air, exiting the evaporator 28 at a high enthalpy and a low pressure. A fan 32 blows air through the evaporator 28. The refrigerant then flows to the compressor 22, completing the cycle.

FIG. 2 shows the evaporator 28. The evaporator 28 includes an inlet manifold 40 and an outlet manifold 42 that extend along an axis X. The inlet manifold 40 includes a body portion 43 and openings 41 and has a length d. A plurality of flat tubes 44 having a length c extend between the manifolds 40 and 42 along an axis Y. The axis X is substantially perpendicular to the axis Y. Each of the openings 41 of the inlet manifold 40 aligns with one of the flat tubes 44.

Refrigerant from the expansion device 26 flows into the inlet manifold 40. The refrigerant from the inlet manifold 40 flows through the openings 41, into the plurality of flat tubes 44 and accepts heat from air 46 flowing over the flat tubes 44. The evaporator 28 can also include a plurality of fins 48 having louvers positioned between the flat tubes 44 to aid in heat transfer between the refrigerant and the air. The refrigerant then flows into the outlet manifold 42 through openings 45 and is directed to the compressor 22 through an outlet opening 70.

As shown in FIGS. 3 and 4, a distributor tube 34 including a short tube 34 a and a long tube 34 b is located in the body portion 43 of the inlet manifold 40. A y-shaped flow splitter 52 is attached to the distributor tube 34. The flow splitter 52 includes an inlet portion 56 and two parallel outlet portions 54 a and 54 b. An inlet tube 50 is in fluid communication with the inlet portion 52, and the short tube 34 a and the long tube 34 b are in fluid communication with the outlet portions 54 a and 54 b, respectively. In one example, the tubes 34 a and 34 b are parallel to each other and to the inlet tube 50.

The tube 34 a includes a first end 62 a connected to the outlet portion 54 a of the flow splitter 52 and an opposing second end 64 a that is blocked by a stop 60 a. The tube 34 b includes a first end 62 b connected to the outlet portion 54 b of the flow splitter 52 and an opposing second end 64 b that is blocked by a stop 60 b. The short tube 34 a has a first length a, and the long tube 34 b has a second length b. That is, the first length a is less than the second length b. The first length a of the short tube 34 a is approximately 30-70% of the second length b of the long tube 34 b, considering the pressure balance within the tubes 34 a and 34 b.

In one example, the second length b of the long tube 34 b is approximately equal to the length d of the inlet manifold 40. However, the second length b of the long tube 34 b can be slightly less than the length d of the inlet manifold 40, such as approximately 94 to 100% of the length d of the inlet manifold 40.

The second end 64 a of the short tube 34 a aligned with a location 71 of the long tube 34 b. That is, the location 71 on the long tube 34 b is substantially between the ends 62 b and 64 b of the long tube 34 b. In one example, the location 71 is substantially in the middle of the ends 62 b and 64 b.

The tubes 34 a and 34 b each include orifices 58 a and 58 b, respectively. The orifices 58 a and 58 b are appropriately sized to cause a pressure drop or a pressure build-up in the distributor tube 34 and to reduce the separation of vapor refrigerant and liquid refrigerant in the two-phase refrigerant flow. The orifices 58 a of the short tube 34 a are linearly aligned and are located in a section 75 defined between the ends 62 a and 64 a of the short tube 34 a. The orifices 58 b of the long tube 34 b are linearly aligned and are located in a section 73 defined between the location 71 and the end 64 b of the long tube 34 b. Therefore, the orifices 58 a and 58 b are located in different sections 73 and 75 of the distributor tube 34. The orifices 58 a and 58 b are aligned such that they extend along a straight line substantially parallel to the lengths a and b of the tubes 34 a and 34 b, respectively.

As shown in FIG. 5, the orifices 58 a direct refrigerant flowing through the short tube 34 a into the inlet manifold 40 at a first direction E, and the orifices 58 b direct refrigerant flowing through the long tube 34 b into the inlet manifold 40 at a second direction F. The refrigerant directed into the inlet manifold 40 is then directed through the openings 41 and into one of the flat tubes 44 for heat exchange with the air at a third direction G.

In one example, the first direction E and the second direction F are oriented at an angle relative to the third direction G. In one example, the first direction E and the second direction F can be oriented at an angle that is approximately 45° to 315° clockwise from the third direction G. However, the orifices 58 a and 58 b can be located at any number of locations and are located in a way that helps to induce and cause additional mixing when the refrigerant is discharged from the tubes 34 a and 34 b.

In one example shown in FIG. 5, the second direction F is approximately 135° clockwise relative to the third direction G, and the first direction E is approximately 225° clockwise (or 135° counter-clockwise) relative to the third direction G.

The refrigerant exiting the expansion device 26 is in two phases and includes approximately 80% vapor and approximately 20% liquid by mass. The density of the liquid refrigerant is approximately 10-100 times greater than the density of the vapor refrigerant. Therefore, the vapor refrigerant flows faster than the liquid refrigerant.

Refrigerant from the expansion device 26 enters the distributor tube 34 through the inlet tube 50 and flows into the tubes 34 a and 34 b. The flow splitter 52 divides the refrigerant entering the inlet manifold 40 such that approximately 50% enters the short tube 34 a and approximately 50% enters the long tube 34 b. As the second ends 64 a and 64 b of the tubes 34 a and 34 b, respectively, are blocked by the stops 60 a and 60 b, respectively, the refrigerant is forced through the orifices 58 a and 58 b and into the inlet manifold 40. The increase in pressure causes the refrigerant to distribute equally along the length d of the inlet manifold 40.

The refrigerant entering the short tube 34 a is equally distributed to the section 75 through the orifices 58 a, and the refrigerant entering the long tube 34 b is equally distributed to the section 73 through the orifices 58 b. The refrigerant is equally distributed to each section 73 and 75 as half of the refrigerant is provided to each tube 34 a and 34 b. An equal distribution of refrigerant is possible as half of the refrigerant is provided to each half of the length d of the inlet manifold 40 for distribution to the flat tubes 44. As a portion of the refrigerant is specifically designated for distribution to a specific section 73 and 75 of the inlet manifold 40, a better distribution of refrigerant is possible in each section 73 and 75 of the inlet manifold 40.

By employing a short tube 34 a and a long tube 34 b, maldistribution of the refrigerant can be prevented, especially if the length d of the inlet manifold 40 is very long, such as greater than 800 mm. For example, if the length d of the inlet manifold 40 is 800 mm, half of the refrigerant would be designated to each 400 mm section of the inlet manifold 40, providing a more even distribution of refrigerant in each 400 mm section, as each 400 mm section is designated to receive half of the refrigerant.

The foregoing description is only exemplary of the principles of the invention. Many modifications and variations of the present invention are possible in light of the above teachings. The preferred embodiments of this invention have been disclosed, however, so that one of ordinary skill in the art would recognize that certain modifications would come within the scope of this invention. It is, therefore, to be understood that within the scope of the appended claims, the invention may be practiced otherwise than as specifically described. For that reason the following claims should be studied to determine the true scope and content of this invention. 

1. A heat exchanger comprising: a plurality of tubes, wherein heat is exchanged between a first fluid and a second fluid in the plurality of tubes; an inlet manifold to direct the first fluid into the plurality of tubes at a third direction; and a distributor tube located within the inlet manifold, wherein the distributor tube includes a short tube including a plurality of first orifices that direct the first fluid into the inlet manifold at a first direction and a long tube including a plurality of second orifices that direct the first fluid into the inlet manifold at a second direction.
 2. The heat exchanger as recited in claim 1 wherein the heat exchanger is a microchannel evaporator.
 3. The heat exchanger as recited in claim 1 wherein the plurality of tubes each include a flattened portion.
 4. The heat exchanger as recited in claim 1 wherein the distributor tube includes a flow splitter that directs half of the first fluid into the short tube and the other half of the first fluid into the long tube.
 5. The heat exchanger as recited in claim 1 further including an outlet manifold, wherein the plurality of tubes fluidly connect the inlet manifold and the outlet manifold.
 6. The heat exchanger as recited in claim 1 wherein the short tube and the long tube are substantially parallel.
 7. The heat exchanger as recited in claim 1 wherein the first fluid enters the short tube and the long tube at a first end, and an opposing second end of each of the short tube and the long tube are blocked with a stop.
 8. The heat exchanger as recited in claim 1 wherein the first fluid is refrigerant and the second fluid is air, and the refrigerant flows through the plurality of tubes and the air passes over the plurality of tubes.
 9. The heat exchanger as recited in claim 1 wherein the plurality of first orifices and the plurality of second orifices are arranged in a linear configuration.
 10. The heat exchanger as recited in claim 1 wherein an angle between the first direction and the third direction is substantially equal to another angle between the second direction and the third direction, wherein the first direction is different from the second direction.
 11. The heat exchanger as recited in claim 10 wherein the angle and the another angle are each approximately 45° to 315° clockwise from the third direction.
 12. The heat exchanger as recited in claim 1 wherein the plurality of first orifices are located in one section of the distributor tube and the plurality of second orifices are located in another section of the distributor tube.
 13. (canceled)
 14. The heat exchanger as recited in claim 12 wherein the first fluid flows through the one section and then through the another section, and there are none of the plurality of second orifices in the one section of the distributor tube.
 15. The heat exchanger as recited in claim 12 wherein the short tube is located in the one section of the distributor tube and the long tube is located in both the one section and the another section of the distributor tube.
 16. A refrigeration system comprising: a compressor for compressing a refrigerant; a condenser for cooling the refrigerant; an expansion device for expanding the refrigerant; and a microchannel evaporator for heating the refrigerant, wherein the microchannel evaporator includes a plurality of tubes, an inlet manifold to direct a first fluid into the plurality of tubes at a third direction, and a distributor tube located within the inlet manifold, wherein the distributor tube includes a short tube including a plurality of first orifices that direct the first fluid into the inlet manifold at a first direction and a long tube including a plurality of second orifices that direct the first fluid into the inlet manifold at a second direction.
 17. The refrigeration system as recited in claim 16 wherein the short tube and the long tube are substantially parallel.
 18. The refrigeration system as recited in claim 16 wherein the first fluid enters the short tube and the long tube at a first end, and an opposing second end of each of the short tube and the long tube are blocked with a stop.
 19. The refrigeration system as recited in claim 16 wherein the plurality of first orifices and the plurality of second orifices are arranged in a linear configuration.
 20. The refrigeration system as recited in claim 16 wherein an angle between the first direction and the third direction is substantially equal to another angle between the second direction and the third direction, wherein the first direction is different from the second direction.
 21. (canceled)
 22. (canceled)
 23. (canceled)
 24. The refrigeration system as recited in claim 21 wherein the short tube is located in the one section of the distributor tube and the long tube is located in both the one section and the another section of the distributor tube. 